The present invention is directed generally to devices for capturing and storing antimatter, and, more particularly, to an antimatter trap that can store relatively large, useful quantities of antimatter in the form of excited positronium, for relatively long times, as implemented by the use of photonic bandgap (PBG) structures. A Bose-Einstein Condensate state of excited positronium can be used to increase the storage density.
The basic building blocks of antimatter are the positively charged electron (positron) and the negatively charged proton (antiproton). Positrons have the same quantum characteristics as electrons, but have a positive electric charge. Antiprotons have the same quantum characteristics as protons, but have a negative electric charge. By combining equal numbers of negative and positive charges, an electrically neutral form of antimatter is constructed. The two simplest forms of electrically neutral antimatter, positronium (Ps) and antihydrogen (Ĥ), are both analogs of the ordinary hydrogen atom (H). Positronium, which has the lowest rest mass of any known atom, consists of a positron and an ordinary electron in orbit around each other. Positronium is formed from a mixture of normal matter and antimatter, and this type of mixed normal matter/antimatter material will hereafter be referred to as exotic matter. Antihydrogen is pure antimatter, consisting of a positron in orbit around an antiproton. Like ordinary hydrogen, both Ps and Ĥ can form molecules (e.g., Ps2 and Ĥ2).
Traps for electrically neutral normal matter particles have been available for many years, see, for example, the loffe-Pritchard Trap and the Time-Averaged Orbiting Potential Trap. Also, Weinstein et al. (xe2x80x9cMicroscopic magnetic traps for neutral atomsxe2x80x9d, Physical Review A, Vol. 52, pp. 4004-4009 (November 1995)) have proposed magnetic microtraps for storing very small amounts of electrically neutral atoms. These neutral atom traps have been difficult to implement as antimatter traps. Positronium is intrinsically unstable because it is composed of a particle and its antiparticle. From the ground state of positronium (e.g., Ps), the electron and positron annihilate in a very short time, generating two (or sometimes three) gamma rays. In free space, Ps self-annihilates in less than one microsecond. Antihydrogen is stable as long as it is confined within a region devoid of ordinary matter, a situation difficult to achieve in devices made of ordinary matter. Current neutral atom traps have a complex implementation, limited efficiency, and limited mass storage capacity. In contrast to the PBG trap of the present invention, current storage devices may have requirements (e.g., large mass, large volume, or high power usage) that preclude their use as an easily mobile trap. Mobility is a useful requirement for many applications of antimatter or exotic matter. For example, Smith et al. note in U.S. Pat. No. 6,160,263, entitled xe2x80x9cContainer for Transporting Antiprotonsxe2x80x9d and issued on Dec. 12, 2000, that xe2x80x9c[a]ntimatter could have numerous commercial applications if it could be effectively stored and transportedxe2x80x9d.
Traps for electrically charged particles have been available for many years, see, for example, the Cyclotron, the Paul Trap, and the Penning Trap. These devices have been used for the storage of electrically charged antimatter. However, they are capable of storing only relatively small amounts of electrically charged matter or electrically charged antimatter. Various proposals and suggestions for storing electrically charged antimatter have been made. For example, U.S. Pat. No. 5,118,950, entitled xe2x80x9cCluster Ion Synthesis and Confinement in Hybrid Ion Trap Arraysxe2x80x9d and issued on Jun. 2, 1992, to John T. Bahns et al., discloses a cluster ion synthesis process utilizing a containerless environment to grow in a succession of steps cluster ions of large mass and well defined distribution. The cluster ion growth is said to proceed in a continuous manner in a plurality of growth chambers which have virtually unlimited storage times and capacities. U.S. Pat. No. 5,206,506, entitled xe2x80x9cIon Processing: Control and Analysisxe2x80x9d and issued on Apr. 27, 1993, to Nicholas J. Kirchner, discloses an ion processing unit including a series of perforated electrode sheets, driving electronics, and a central processing unit, forming a variant of the well-known non-magnetic radio frequency quadrupole ion trap. Kirchner suggests that as electrically charged antimatter is produced, it can be introduced into each processing channel and held confined to an individual potential well. However, Kirchner does not provide a mechanism for the effective introduction of the electrically charged antimatter into his device, and he makes no mention of the critical vacuum requirements.
In another example, U.S. Pat. Nos. 5,977,554 and 6,160,263, both entitled xe2x80x9cContainer for Transporting Antiprotonsxe2x80x9d and issued on Nov. 2, 1999, and Dec. 12, 2000, respectively, to Gerald A. Smith et al., and U.S. Pat. No. 6,414,331, entitled xe2x80x9cContainer for Transporting Antiprotons and Reaction Trapxe2x80x9d and issued on Jul. 2, 2002, to Gerald A. Smith et al., disclose a container for transporting antiprotons, including a dewar having an evacuated cavity and a cryogenically cold wall. A plurality of thermally conductive supports is disposed in thermal connection with the cold wall and extends into the cavity. An antiproton trap is mounted on the extending supports within the cavity. A scalable cavity access port selectively provides access to the cavity for selective introduction into and removal from the cavity of the antiprotons. The container is capable of confining and storing antiprotons while they are transported via conventional terrestrial or airborne methods to a location distant from their creation. An electric field is used to control the position of the antiprotons relative to the antiproton confinement region.
These discussions pertain to the storage of antiprotons or positrons, but none discloses or suggests a method for the storage of electrically neutral antimatter or electrically neutral exotic matter (in particular, excited positronium, Ps*) in an easily mobile form. There remains a need for an antimatter trap that can store relatively large quantities of electrically neutral antimatter or exotic matter in a relatively small package with relatively low power requirements. The PBG trap of the current invention could be used in combination with one of these conventional traps with considerable synergistic results. Indeed, as suggested by Michael M. Nieto et al., xe2x80x9cDense Antihydrogen: Its Production and Storage to Envision Antimatter Propulsion,xe2x80x9d Los Alamos Report LA-UR-01-3760, pp. 1-12 (Dec. 12, 2001), xe2x80x9c . . . a space-certified storage system for neutral antimatter can not be obtained from a linear extrapolation of heretofore existing technologiesxe2x80x9d.
When a particle, such as an electron, collides with its corresponding antiparticle (in this case the positron), the two particles annihilate and convert their total mass into energy. Thus, antimatter or exotic matter exists in the terrestrial environment only for very brief periods. There are many sources of positrons, e.g., commonly available radioactive isotopes such as 22Na which exhibit xcex2+-decay, and positron/electron pair creation by high-energy gamma rays produced by electron beams or as a by-product of neutron capture processes such as 113Cd(n,xcex3)114Cd*. In this neutron capture process, the 114Cd* decays by emitting two or more gamma rays that can subsequently produce electron/positron pairs in a moderator such as tungsten (Richard Howell, xe2x80x9cThe Future: Intense Beamsxe2x80x9d, in Positron Beams and Their Applications, ed. Paul Coleman, World Scientific: Singapore, pp. 307-322, 2000). However, the production of antiprotons (and hence antihydrogen) is limited to very high-energy collision processes carried out in very expensive, complex facilities such as accelerators. Another important differentiating property between positron-based exotic antimatter (e.g., Ps) and antiproton-based antimatter (e.g., Ĥ) is the difference in the critical temperatures at which Ps and Ĥ transition to a Bose-Einstein Condensate (BEC). For Ps, the critical temperature can be as high as the easily achieved value of 300 degrees Kelvin, as discussed in D. B. Cassidy and J. A. Golovchenko, xe2x80x9cThe Bose-Einstein Condensation of Positronium in Submicron Cavitiesxe2x80x9d, in New Directions in Antimatter Chemistry and Physics, eds. C. M. Surko and F. A. Gianturco, Kluwer: Netherlands, pp. 83-99, 2001. For Ĥ, the critical temperature is below one degree Kelvin, a situation achievable only with complex, expensive apparatus. Forming a BEC is of importance in achieving a high storage density. These contrasting properties of Ps and Ĥ make it clear that Ps is the more important form of antimatter or exotic matter for practical applications within the present framework of our technological and financial environment. However, most workers have dismissed attempts to stabilize Ps because, like many things in nature, the first level of consideration appeared to give a negative result (Ps self-annihilates from the ground state in less than a microsecond), but further investigations and new technological discoveries supercede the old ideas.
Several references in the scientific literature discuss the use of Bose-Einstein Condensation to promote the storage of Ĥ and/or Ps, see, e.g., Allen P. Mills Jr., xe2x80x9cPositronium molecule formation, Bose-Einstein condensation and stimulated annihilationxe2x80x9d, Nuclear Instruments and Methods in Physics Research B, Vol. 192, pp. 107-116 (May 2002); P. M. Platzman and Allen P. Mills Jr., xe2x80x9cPossibilities for Bose condensation of positroniumxe2x80x9d, Physical Review B, Vol. 49, pp. 454-458 (January 1994); D. B. Cassidy and J. A. Golovchenko, xe2x80x9cThe Bose-Einstein Condensation of Positronium in Submicron Cavitiesxe2x80x9d, in New Directions in Antimatter Chemistry and Physics, eds. C. M. Surko and F. A. Gianturco (Kluwer: Netherlands), pp. 83-99 (2001); Haruo Saito and Toshio Hyodo, xe2x80x9cCooling and Quenching of Positronium in Porous Materialxe2x80x9d, in New Directions in Antimatter Chemistry and Physics, eds. C. M. Surko and F. A. Gianturco (Kluwer: Netherlands), pp. 101-114 (2001); and Michael M. Nicto et al., xe2x80x9cDense Antihydrogen: Its Production and Storage to Envision Antimatter Propulsionxe2x80x9d, Los Alamos Report LA-UR-01-3760, pp. 1-12 (Dec. 12, 2001). However, these authors do not suggest a mechanism or apparatus for extending the lifetime of the stored Ps beyond the natural limit of less than a microsecond. Thus, these authors generally assume that they must work within the constraints imposed by this very short natural lifetime.
Using well-established mathematical models of physical laws, it has been shown that externally applied crossed electric and magnetic fields could be used to extend the lifetime of positronium (Ps) by many orders of magnitude (J. Ackermann et al., xe2x80x9cLong-Lived States of Positronium in Crossed Electric and Magnetic Fieldsxe2x80x9d, Physical Review Letters, Vol. 78, pp. 199-202 (13 Jan. 1997); P. Schinelcher, J. Ackermann, and J. Shertzer, xe2x80x9cStabilization of matter-antimatter atoms in crossed electric and magnetic fieldsxe2x80x9d, Nuclear Instruments and Methods in Physics Research B, Vol. 143, pp. 202-208 (1998); J. Shertzer et al., xe2x80x9cPositronium in crossed electric and magnetic fields: The existence of a long-lived ground statexe2x80x9d, Physical Review A, Vol. 58, pp. 1129-1138 (August 1998)). However, the authors do not provide a means for confining and storing large quantities of Ps, and their proposed apparatus calls for magnetic field strengths in excess of 10 T. Such magnetic field strengths are not amenable to easily mobile devices, as they require substantial laboratory equipment and power. It is possible to combine the method of Ackermann, Schmelcher, and Shertzer with the device of the present invention, with synergistic results. It has been predicted that externally applied laser fields could be used to extend the lifetime of ground-state Ps by up to a factor of 20 (Antonella Karlson and Marvin Mittleman, xe2x80x9cStabilization of positronium by laser fieldsxe2x80x9d, Journal of Physics B, Vol. 29, pp. 4609-4623 (1996)). Karlson and Mittleman do not provide a means for confining and storing large quantities of Ps, nor do they provide a means for extending the lifetime of Ps by many orders of magnitude. However, the technique of Karlson and Mittleman has synergistic potential with the present invention.
No patents have been found which disclose any method or apparatus for storing massive amounts of Ps for times longer than the natural sub-microsecond lifetime. Two patents are found (U.S. Pat. No. 4,867,939, entitled xe2x80x9cProcess for Preparing Antihydrogenxe2x80x9d and issued on Sep. 19, 1989, to Bernhard I. Deutch, and U.S. Pat. No. 6,163,587, entitled xe2x80x9cProcess for the Production of Antihydrogenxe2x80x9d and issued on Dec. 19, 2000, to Eric A. Hessels) that show how one might construct Ĥ, but the inventors do not disclose any method or apparatus for storing, and transporting to a location distant from its creation, Ĥ or other species of antimatter or exotic matter.
There are many applications that would benefit from the development of an antimatter trap with the following desirable characteristics. The trap should store relatively large quantities of antimatter, should store electrically neutral species, should allow controlled release of the antimatter, and should have minimal size and power requirements making the device amenable to transportation. The device of the present invention is the only method that achieves these characteristics. The device of the present invention can supply enough antimatter to make a gamma-ray laser, or to initiate a controlled nuclear fusion reaction.
In accordance with the present invention, an antimatter storage device for electrically neutral excited species of antimatter or exotic matter is provided. The antimatter storage device comprises a three-dimensional or two-dimensional photonic bandgap (PBG) structure containing at least one PBG cavity in the PBG structure. The PBG cavity comprises a cavity wall embedded in the PBG structure and is surrounded by the PBG structure. The cavity contains a quantity of species selected from the group consisting of excited electrically neutral atoms and molecules of antimatter, and excited electrically neutral atoms and molecules of exotic matter.
Further in accordance with the present invention, a method of capturing antimatter is provided. The method comprises:
providing an antimatter capture device comprising the three-dimensional or two-dimensional PBG structure above; and
introducing the species into at least one PBG cavity.
Also in accordance with the present invention, a method for exciting antimatter species to an excited state is provided. The method comprises:
providing an antimatter excitation device comprising the three-dimensional or two-dimensional PBG structure above; and
exciting said species.
Still further in accordance with the present invention, a state of antimatter is provided, comprising the three-dimensional or two-dimensional PBG structure above, containing an array of PBG cavities. Each PBG cavity is separated from its nearest-neighbor cavities by a distance that is less than the photon localization length. Each cavity contains a quantity of the species.
Also in accordance with the present invention, a stable form of exotic matter is provided, comprising excited states of positronium (Ps*), confined within the cavities in the PBG structure, isolated from other electrons.
Yet further in accordance with the present invention, a combination of localized photons and partially excited species is provided, which forms a stationary-state superposition thereof, or a stable photon-species-cavity bound state, formed by an excited electrically neutral species of antimatter or exotic matter interacting with the cavity walls of the cavity located within the PBG structure. The interaction is mediated by photons.
Also in accordance with the present invention, a method of releasing gamma ray radiation is provided. The method comprises:
providing the antimatter excitation device above, the PBG cavity containing a quantity of excited positronium; and
perturbing the PBG structure such that the index of refraction contrast, the geometry, the spacing, and/or the shape of the constituent components changes in such a way as to shift or turn off the bandgap that is responsible for maintaining the positronium in an excited state to thereby release the gamma ray radiation.
Still further in accordance with the present invention, a beam of species is provided, comprising excited electrically neutral atoms or molecules of antimatter or exotic matter emitted by the PBG structure above, where each PGB cavity contains a quantity of the species. The beam comprises the species channeled out of the PBG structure into a desired direction by opened linear defect waveguides in the PBG structure.
Finally, a particle beam is provided, comprising electrically charged antimatter emitted by the PBG structure. Each PBG cavity contains a quantity of excited electrically neutral atoms or molecules of antimatter or exotic matter, which are then ionized by an electric field, producing positively and negatively charged ions. In the case of positronium, this separates each positronium atom into its constituent positron and electron. Electric and magnetic fields are used to direct the ions or antimatter and/or normal matter out of the PBG device and into the desired direction.